为什么此代码显示 StackOverflow 错误？

Question

import java.util.Arrays;
import java.util.Scanner;


public class EqualMedian {

    static int median(int[] a, int[] b, int mid, int[] temp) {
        int count = 0;

        if (a[mid] != b[mid]) {
            temp[0] = a[mid];
            a[mid] = b[mid];
            b[mid] = temp[0];

            Arrays.sort(a);
            Arrays.sort(b);
            count++;
            median(a, b, mid, temp);
        }

        return count;
    }

    public static void main(String args[]) throws Exception {
        Scanner sc = new Scanner(System.in);
        int t = sc.nextInt();

        for (int j = 0; j < t; j++) {
            int n = sc.nextInt();
            int a[] = new int[n];
            int b[] = new int[n];

            for (int i = 0; i < n; i++) {
                a[i] = sc.nextInt();
            }

            for (int i = 0; i < n; i++) {
                b[i] = sc.nextInt();

            }

            int[] temp = { 0 };
            int mid = (n / 2) + 1;
            int ans = median(a, b, mid, temp);
            System.out.println(ans);

        }
    }
}

OUTPUT: Execution failed. Stack Trace: Exception in thread "main" java.lang.StackOverflowError at java.util.DualPivotQuicksort.sort(DualPivotQuicksort.java:111) at java.util.Arrays.sort(Arrays.java:144) at Equal_median.median(Equal_median.java:16) at Equal_median.median(Equal_median.java:19) Equal_median.median(Equal_median.java:19) at Equal_median.median(Equal_median.java:19)

Answer 1

您只是交换 a[mid] 和 b[mid] 并且它们永远不会相等，它将以无限递归调用结束，因此会出现 stackocverflow 错误。

Answer 2

So your final goal is to determine if 2 arrays have equal median, and if so, print the median? You should make a method that computes the median for only one array. Call this method for each array in main. No need for recursion.

public static int median(int []myArray) {
    int mid = (myArray.length() / 2) + 1;
    return myArray[mid]
}

public static void main(String args[]) {
    ...
int firstMedian = median(a);
int secondMedian = median(b);
    if(firstMedian == secondMedian) {
        System.out.println(firstMedian);
    }
}

Recursion should not be used without setting proper ending conditions. So.. always double-check your condition. Most recursions have a for/while loop equivalent. If the condition in a while loop sounds like it will go to infinity, it's probably a bad idea.

Also, if a variable can be computed locally and serves no purpose after the method (such as temp ), don't make it a parameter! Just declare it locally.